Brazing solder



, Zinc is the most common of these.

Patented Aug. 8, 1944 BBACZING SOLDER Melvin M. Goldsmith, Chicago,111., aslltnor to Goldsmith Bros. smelting & Refining Company, acorporation of West Virginia No Drawing. Original application March 3,1941, Serial No. 381,595, now Patent No. 2,310,231, dated February 9,1943. plication May 6,, 1942, Serial No. 441,967

3 Claims. (Cl. 75-155) This invention relates to an improved brazingsolder.

Brazing solders, or hard solders are employed for soldering purposeswhere the ordinary soft Divided and this apand a small amount of bore:sufllclent to bind the particles of charcoal together.

It is possible to incorporate the sodium with the silver, although onaccount of the high meltsolders have not suflicient strength, or do notns Point the Silver this is not 80 desirablehave sufficient corrosionresistance. Such brazing solders preferably have a melting point as lowas 1175 F. or thereabouts, although in some cases they are prepared withmelting points as high as 1350" F The basis of most brazing solders issilver, although in many of them copper predominates.

Silver and copper are employed in order to give strengthto the solder,but the'melting points of these metals, or mixtures of them, are toohigh for the purposes desired. Therefore, various metals have been usedto lower the melting point. Zinc alone, however, has a tendency to makethe solder non-v free flowing or stiif, and other metals are frequentlyused to make the solder flow more freely. Cadmium is a typical exampleof such a metal. Silver and zinc form a eutectic with about 4 to 1 ratioof silver to zinc. Although the presence of other metals affects theeutectic ratio considerably, in preparing the present alloy or solder itis preferred that silver predominate greatly over the zinc. Inaccordance with the present invention the melting point ofsilver-containing brazing solders is lowered markedly by the inclusiontherein of a very small percentage of sodium metal. The amount of thesodium is ordinarily 1% to 2%,

and should be less than 5%. Strangely enough, while sodium does notmarkedly lower the melting point of silver or zinc when added to either.of them in small' proportions, a minor amount does markedly affect asilver copper alloy, particularly in the presence of zinc. Even amountsas low as 0.05% markedly affect the solder. In

' addition to its advantage in lowering the meltin point, however, thesodium makes the solder extremely penetrating, partially because it ispossible to eliminate considerable zinc. It also reduces the tendency tooxidation, and the potential the use of sugar, which promptly formscharcoal,

alkalinity of the sodium is of value in counter- Where an exclusivelysilver sodium, and copper material is employed this procedure should befollowed, however, because the sodium does not readily combine.

The following areexamples of alloys containing phosphorus:

Per cent This application is continuation-in-part of my co-pe'ndingapplication Serial No. 261,345, filed March 11, 1939. and a division ofmy copending application 381,595, filed March 3, 1941.

The'foregoing detailed description has been given for clearness ofunderstanding only, and no unnecessary limitations should he understoodtherefrom.

What I claim asnew, and desire to secure by Letters Patent, 18:

1. A solder consisting essentially of:

7 Per cent Silver 10 to 15 Cadmium 10 to 15 Copper 55 to Zinc 7 to 12Sodium 0.05to 1.0

Phosphorus 0.04to 1.5

' the amount of impurities being ineui'flcient to '3. Aaolder consistingessentially oi 10% to 15% alter the essential properties of the alloy.of silver; 0.2% to 1.5% of sodium; the balance 2. A solder consistingessentially of: being copper, cadmium, zinc and phosphorus. e Per centthe copper vbeing at least 55% of the total, the 13.5 I phosphorus notexceeding 1.5%, the zinc not ex-' Siiver m um, 1 ceeding 12%, the coppernot exceeding 85%, and Zinc r r 835 the cadmium not exceeding 15%.

opper I 82.0 1 7 Sodium 0.25 'MELVIN M. GOLDSMITH.

Phosphorus 1.5

